This invention relates to a pipe flange and more particularly to a type of pipe flange known as a convoluted flange. Pipe flanges are used to interconnect pipe sections and fittings to other pipe sections and fittings of various types. A convoluted flange utilizes a design in which an annular flange member has a U-shaped cross section to provide strength to the flange, which is reduced in weight and material content with resultant cost savings. A convoluted flange is described in Shultz, U.S. Pat. No. 4,484,771, issued Nov. 27, 1984. In that reference, a convoluted flange rim is described that is fabricated from a disk blank in a press. The thickness of the annular convoluted flange rim is therefor uniform. The flange rim is slipped over the end of a pipe section and retained by a flared end face that provides the contact or sealing face for an opposed flange on a pipe section or fitting. The convoluted flange rim provides the bolting ring to the flange rim of the mating fitting.
To prevent deformations in the flange rim of the lighter weight prior art convoluted flange from being transmitted as stresses to the pipe weldment, the outer periphery of the U-shaped rim contacts the abutting face of the opposing flange. This contact provides strength for mechanical support of the pipe connection without excessively stressing the pipe at or above the weld to a flared stub end fitting for seating the flange rim. This method of managing stresses in the prior art flange restricts the type of seals that can be used and requires great precision in selecting a seal according to proper thickness.
Conventional flanges are cast and ordinarily are relatively thick to prevent warpage on bolting. Because cast flanges are relatively inexpensive to produce, various systems have been devised to construct convoluted flanges with a cast metal flange rim. U.S. Pat. No. 4,458,924 of Schlicht, issued Jul. 10, 1984 entitled, "Bimetal Flange Connector" describes one such flange with a ductile iron convoluted flange rim. While the weight of the bimetal flange is reduced over conventional flanges, the process of fabricating the bimetal flange is more complicated and costly than conventional cast or forged flanges.
This inventor has constructed useful cast convoluted flanges that have the advantages of the Shultz flange without the requirement that the periphery of the flange rim contact the opposing flange face. However, to provide for the structural integrity for the physical connection to the connected flange, the cast convoluted flange is of greater thickness, thereby compromising the advantages of lighter weight and reduced material requirement characteristic of a convoluted flange. Furthermore, the added thickness results in a build-up of stresses transmitted to the pipe weldment making this design less than an ideal solution.
It is an object of this invention to provide a light-weight convoluted flange that is designed and configured to provide all of the advantages of a convoluted flange in an inexpensive casting or forging with controlled management of stresses. The objective is accomplished by using transitional changes in thickness of the flange member. The improved convoluted flange has greater flexibility and allows the flange bolts to compress a seal interposed between the compression faces with the desired force to effect proper sealing without transmitting excess stresses to the flange stub or pipe weldment.
Another object of this invention is to provide a flange assembly that includes a trapped flange seal and utilizes a convoluted flange member, preferably of the type that includes controlled management of stress. The trapped seal flange assembly is particularly useful for piping systems carrying abrasive slurries and eliminates turbulence that abrades the inside surface of the pipe. The trapped seal is also desirable for systems where it is necessary to minimize contact of the medium in the pipe with the seal, particularly a seal that may otherwise extrude into the piping passage on tightening of the flange bolts.
Another object of this invention is to provide a flange assembly where the flange rim through which the tightening bolts pass is rotatable on the pipe end for ease of alignment with the holes on the opposed flange to which it connects, and where the flange rim has a convoluted design that does not require the outer lip from contacting the opposed flange, thereby allowing for use of a greater variety of flange seals.